COL5A1 and Ehlers-Danlos syndrome: Heterotrimeric collagen V fibrils regulate the diameter of fibrillar collagen I fibrils in skin (Wenstrup et al., 2004) and mutations in COL5A1 and COL5A2 can result in classic Ehlers-Danlos syndrome, characterized by fragile skin, hyperextensible skin and impaired wound healing.